The present invention relates to a conduit coupling assembly for connecting multiple lengths of conduit in coaxial or end-to-end relationship. It is a conventional practice in many types of pipe or conduit systems, and particularly in electrical systems employing tubular conduits that contain electrical wires or cables, to connect a number of lengths of conduit in end-to-end relation through means of couplings so as to form a continuous conduit system as necessary for a particular application. In the case of thin wall conduit, which is primarily employed for encasing electrical cable or conductor wires in applications where the conduit will not be subjected to large stresses, compression fittings or coupling assemblies may be employed which are swaged or otherwise affixed to adjacent ends of conduit lengths. The conduit is generally available in different lengths and may be quite readily formed to various bend contours and coupled end-to-end through the compression couplings or coupling assemblies.
One known technique for connecting lengths of conduit in coaxial or end-to-end relationship is to provide external threads of standard size on the opposite ends of each length of conduit and then connect the lengths of conduit through coupling assemblies. Those coupling assemblies have internal threads, which enable threaded connection with adjacent ends of the conduit lengths to form a structurally sound and electrically sound connection. One known coupling assembly for coupling lengths of conduit is disclosed in commonly assigned U.S. Pat. No. 4,957,314 to Basile et al. The coupling assembly disclosed in the Basile et al. patent requires specially manufactured components, including outer and inner coupling assemblies that must be first installed on each length of conduit before the lengths of conduit can be coupled together. More specifically, the coupling assembly utilizes outer and inner coupling members having threaded ends for threading onto the ends of the lengths of conduit. The outer coupling member is threaded or screwed on to one end of one length of conduit and the inner coupling member is threaded or screwed onto one end of the other length of conduit. The lengths of conduits are then axially aligned and the inner coupling member is inserted into the outer coupling member. The inner coupling member is firmly held in the outer coupling member by set screws disposed on the outer coupling member.
Other known coupling assemblies are disclosed in commonly assigned U.S. Pat. Nos. 4,547,004 to Goldberg and 4,592,574 to Vollmuth et al. Similar to the coupling assembly disclosed in the Basile et al. patent, the coupling assemblies disclosed in the Goldberg and Vollmuth et al. patents require specially manufactured components, including outer and inner coupling members that must be first installed on one length of conduit before the lengths of conduit can be coupled together. Those outer and inner coupling members have threaded ends and the lengths of conduit are subsequently joined by rotating the outer coupling member to thread or screw it onto the other end length of conduit.
Another known technique for connecting lengths of conduit is to provide lengths of conduit with built in set screw assemblies. More specifically, each length of conduit includes a receiving end having an enlarged bell portion or increased diameter that is shaped and configured to receive the insertion end of another length of conduit. In addition, set screws are disposed in apertures located on the bell portion and are used to mechanically hold the insertion end in the bell portion. During installation, the insertion end is positioned in the bell portion and the set screws in the bell portion are advanced or tightened until it engages the insertion end to firmly hold the insertion end in the bell portion. Such a coupling assembly has many advantages over other known techniques for connecting lengths of conduit. For example, such a coupling assembly eliminates the need for multiple components, such as outer and inner coupling members. Thus, the increased cost and time associated with the inventory, shipping, and factory and field installation of the multiple components is eliminated.
Even though those built in set screw coupling assemblies have many advantages over other known techniques for connecting lengths of conduit, improvements in those set screw coupling assemblies are needed. For example, a need exists for a built in set screw coupling assembly that (1) reduces the amount of time needed to tighten the screws or bolts during the conduit installation process, (2) reduces or eliminates the amount of offset typically caused when several conduits are assembled and joined together, (3) reduces or eliminates the amount of dimpling or denting that may occur on the insertion end of the length of conduit when the set screws are tightened, (4) reduces or eliminates the possibility that a set screw will vibrate loose from the tightened position, (5) increases the mechanical connection between the lengths of conduit, and (6) increases the safety of the conduit system by eliminating or reducing any damage of the electrical cable at the connection joint between the length of conduit. Those improvements, among others, are found in the present invention.